Protections are known of the type comprising:                a substantially tubular body which extends in a longitudinal direction and which is intended to be adjusted around said limb and which has an aperture which extends in the longitudinal direction,        a rigid tongue which is intended to cover a front portion of the body which extends at one side and the other of said aperture,        a strap which extends transversely to the longitudinal direction between the edges of the aperture, said strap being connected to the body at one side and the other of the aperture in an adjustable manner in order to adjust the spacing between the edges of the aperture.        
In order to adapt to the various morphologies of the users, the geometry of the boot must be adaptable with a relatively large adjustment range. Of course it is desirable for maximum protection to be provided for all users. Furthermore, for reasons of weight, ease of use and price, the assembly must be relatively simple.